In Syria, the battle for Aleppo looks to be heading for its conclusion. It could still be some days away but pro-government forces now seem to have the momentum and an unassailable advantage.

Meanwhile, Kurdish and Arab militias, backed up by Western air power, have begun isolating IS's de facto capital, Raqqa.

And in Iraq, the battle to liberate the so-called Islamic State stronghold of Mosul is joined. Iraqi troops have begun the slow and deadly process of clearing the city block by block.

These three battles for these three cities promise to significantly alter the course of the conflicts in Iraq and Syria.

Their conclusion will mark a turning point in what has become a major regional struggle.

But will the defeat of IS in Mosul and Raqqa, or the recapture of Aleppo by the Syrian government, actually bring peace any closer?

The grim truth is that they may simply herald the next equally bitter stage in the conflict.

Assad's limits

The plight of Aleppo and its citizens has highlighted the brutality of the Syrian conflict, along with the inability of Western and Arab external actors to influence the situation on the ground.

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Iraqi soldiers take cover during an operation against IS in Intisar, eastern Mosul

If and when pro-government forces retake the eastern part of the city in its entirety, it will send a powerful signal that President Bashar al-Assad's government is not going away.

He will rule over a rump western Syria, while various disparate rebel militias opposed to him control other areas of the country.

Groups linked to IS or al-Qaeda may remain the strongest fighters, with so-called moderates uncertain what support they will get from US President-elect Donald Trump's incoming administration.

It is a recipe for chaos and anarchy.

Of course, a lot depends upon what President Assad does next.

Does he really want - as he says - to take back all of the territory he has lost?

If so, he simply does not have the personnel to do this: a problem with deeper ramifications, which I will come to in a moment.

This is also likely to put him at loggerheads with his backers in Moscow.

Moscow's goals

Russia has succeeded in its strategic goal, to preserve President Assad in power and thus consolidate and expand its diplomatic toe-hold in the Middle East.

Russia has used the Syrian campaign both to brandish its military power and to provide a shop-window for its arms sales.

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Much now depends on what presidents Assad and Putin decide to do next

But might Russia want to "cash in" its success now, for example, by seeking some sort of deal with the new Trump administration?

So far, the preservation of Mr Assad and Moscow's strategic interests have gone hand in hand. But this may not always be the case.

Russian air power has been decisive in securing Mr Assad's future. But so, too, has outside support, principally from Iran and from a variety of pro-Iranian militia forces, not least Hezbollah fighters from Lebanon.

Indeed, over the course of the conflict, the Syrian military machine has broken.

Losses have prompted fragmentation.

Many of its "units" have turned into little more than loyalist militias.

They do not have the numbers to seize and hold all of the territory lost to the rebels.

Iran's voice in Syria has inevitably become much stronger, (as it has, to an extent, in Iraq, due to the counter-IS struggle).

This is something the incoming US administration will have to reckon with if it seeks any kind of arrangement with Russia, since it would essentially be accepting Iran's ever-stronger position.

Legacy of ruins

All the signs are that the Trump administration's central concern is counter-terrorism.

So will it seek a counter-IS understanding with Moscow, and will it bolster support for so-called moderate groups on the ground - the same elements that the Obama administration has been supporting?

Once Aleppo is secured by pro-government forces, what then in the rump government-controlled areas?

Many of Syria's cities and much of its infrastructure have been destroyed.

It needs vast funds to rebuild, money that the isolated President Assad will not be able to raise.

It is not just finance but human capital, too.

So many people have left, or are internally displaced, that the country does not have the human capital to rebuild, even if there were a modicum of peace.

Turkish concerns

There is, of course, another external player in Syria, Turkey.

It occupies a significant zone inside northern Syria.

Indeed, this is fast becoming the embryonic safe haven that Ankara has long wanted to establish.

Turkey also threatens to become involved in the struggle for Raqqa.

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People return to their homes in Hisha, north of Raqqa

Turkish-backed rebels have already clashed with US-backed Kurdish fighters, something that Washington sees as a dangerous distraction to the Raqqa campaign.

Turkey's motives are complex.

Its primary concern is to thwart Kurdish unity and any desire for Kurdish separatism in Turkey itself.

But, beyond this, the Turkish president is fond of reminding the world that places such as Mosul and Raqqa were once Ottoman.

This may not imply that he seeks to control them today but it does underscore Ankara's desire to supervise closely what it regards as its strategic hinterland.

In this sense, quite apart from Turkish-Kurdish rivalries, the stage is being set for a battle between Ankara and Tehran for influence in Syria.

The Kurdish genie is now very much out of the bottle.

Internal Kurdish divisions may well thwart their larger ambitions.

But they have one thing going for them.

They tend to be among the most capable fighters on the ground, which is why, despite Turkey's concerns, the US has backed them.

But the Kurds' prominence brings other problems, too.

The advance on Mosul in Iraq has already prompted evictions of Sunni Arabs by Kurdish fighters and the destruction of their homes.

Lasting grievances

The role of Iranian-backed militias in the offensive similarly concerns many in the Sunni population, as it does many of the main Arab players, such as Saudi Arabia.

Some Sunni tribal fighters have joined the campaign against IS but this has only highlighted once again the fundamental problems of governance and inclusion in Iraq.

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What does defeating the so-called Islamic State actually mean?

They are hoping that their role in the campaign affords them greater recognition once IS is defeated.

Mosul may well be captured, and Raqqa, too, might eventually fall.

But that will in no sense mean the end of IS.

Already, there is a lot of discussion in the West about the threat from returning foreign jihadists and the likelihood of IS seeking to step up attacks in Europe and elsewhere.

IS elements will, of course, remain in Syria and Iraq, too.

What exactly "defeating" IS means is also unclear.

For in many ways it is an abstraction - an idea - born out of the failure of the new Shia-dominated Iraqi state to fulfil its commitments to good governance and inclusion of the Sunni minority.

In this sense, the Iraqi government's own policies: the evictions by Kurdish forces - and the threat from pro-Iranian militias - are all recreating the very conditions that prompted the eruption of IS in the first place.